Size detection device capable of automatically rejecting unqualified products

The utility model discloses a size detection device capable of automatically rejecting unqualified products, which belongs to the technical field of motor shaft production detection and comprises a workbench provided with a storage channel. A conveying mechanism and a detection mechanism are mounted at the top of the workbench; the screening mechanism is placed at the bottom of the workbench; the conveying mechanism comprises a first air cylinder, a fixing block, a base, a sliding rail, a second air cylinder, a supporting plate and an air claw. The first air cylinder and the sliding rail are fixedly connected to the top of the workbench, the output end of the first air cylinder is fixedly connected with the fixing block, the fixing block is fixedly connected with the base, the base is slidably connected with the sliding rail, the top of the base is fixedly connected with the second air cylinder, the output end of the second air cylinder is fixedly connected with the middle of the supporting plate, and the two